Just adding some comments for clarity.

CustomWidgets/ExportQueueItemWindow.cs

@@ -210,7 +210,7 @@ namespace MatterHackers.MatterControl
 			if (streamToSaveTo != null) 
 			{
 				streamToSaveTo.Close ();
-				Close ();
+				Close();
 			}
 			// windows vista +: filePathToSave 'test.stl'
 			// windows xp: filePathToSave 'test'

PartsSheet.cs

@@ -241,7 +241,10 @@ namespace MatterHackers.MatterControl
             }
 			try
 			{
+                // save the final document
             	document.Save(pathAndFileToSaveTo);
+                // Now try and open the document. This will lanch whatever PDF viewer is on the system and ask it 
+                // to show the file (at least on Windows).
             	Process.Start(pathAndFileToSaveTo);
 			}
 			catch {